With the rapid development of an information-intensive society, electronic equipment such as PCs, mobile phones and notebooks have already become immensely popular. Electromagnetic waves are radiated from such equipment over various frequency bands, and the presence of such radiation in the environment is rapidly increasing. These electromagnetic waves are not only capable of interfering with the normal functioning of electronic equipment, but are also believed to be potentially harmful to human health. This kind of problem is often called the EMI effect. To solve the problem, an EMI shield is frequently employed as part of the structure of various electronic equipment. The EMI shield can absorb and cut off the propagation of electromagnetic waves, whether coming from outside the equipment or emanating from within the equipment.
A common structure of an EMI shield utilizes one or more metallic films as electromagnetic wave absorbing materials. The metallic films can absorb electromagnetic waves coming from outside, and thereby prevent wave propagation thereof into the equipment. Similarly, electromagnetic waves coming from within the equipment can be absorbed, thereby preventing wave propagation thereof out to other electronic equipment. The absorbed electromagnetic waves encounter electrical resistance, and are eventually converted to heat. Standard requirements of an EMI shield are as follows:                (a) Good electrical conductivity, in order to thoroughly cut off the propagation of electromagnetic waves.        (b) A wear resistant surface that protects the metallic films from abrasion and damage.        (c) Good thermal conductivity in order to avoid heat buildup.        (d) A low weight and thinness.        
Because the wear resistance of metallic films is relatively poor, it is common for wear resistant ceramics or polymers to be coated on the surfaces of metallic films in order to protect the metallic films from abrasion and damage. Ceramic coating materials include oxide, nitride, carbide ceramics. However, both ceramics and polymers have poor electric conductivities that reduce the performance of the EMI shield. The thermal conductivities of these materials are also low, and the resultant heat buildup can cause unduly high temperatures. In addition, the thickness of a ceramic coating is generally from several tens of micrometers (μm) to hundreds of micrometers, which increases the thickness and weight of the electronic equipment.
In consideration of these problems, what is needed is an EMI shield with a wear resistant surface, good electric and thermal conductivities, a thin configuration, and a low weight.